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Trilobite Genera
Trilobites (; meaning "three-lobed entities") are extinct marine arthropods that form the class Trilobita. One of the earliest groups of arthropods to appear in the fossil record, trilobites were among the most successful of all early animals, existing in oceans for almost 270million years, with over 22,000 species having been described. Because trilobites had wide diversity and an easily fossilized mineralised exoskeleton made of calcite, they left an extensive fossil record. The study of their fossils has facilitated important contributions to biostratigraphy, paleontology, evolutionary biology, and plate tectonics. Trilobites are placed within the clade Artiopoda, which includes many organisms that are morphologically similar to trilobites, but are largely unmineralised. The relationship of Artiopoda to other arthropods is uncertain. Trilobites evolved into many ecological niches; some moved over the seabed as predators, scavengers, or filter feeders, and some swam, feeding o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cambrian
The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordovician Period 486.85 Ma. Most of the continents lay in the southern hemisphere surrounded by the vast Panthalassa Ocean. The assembly of Gondwana during the Ediacaran and early Cambrian led to the development of new convergent plate boundaries and continental-margin arc magmatism along its margins that helped drive up global temperatures. Laurentia lay across the equator, separated from Gondwana by the opening Iapetus Ocean. The Cambrian marked a profound change in life on Earth; prior to the Period, the majority of living organisms were small, unicellular and poorly preserved. Complex, multicellular organisms gradually became more common during the Ediacaran, but it was not until the Cambrian that fossil diversity seems to rapidly ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proetida
Proetida is an order of trilobite that lived from the Ordovician to the Permian. It was the last surviving order of trilobite, dying out in the Permian-Triassic extinction event. Description These typically small trilobites resemble those of the order Ptychopariida, from which the new order Proetida was separated in 1975 by Richard Fortey, Fortey and Owens. Like the order Phacopida, the proetids have exoskeletons that sometime have pits or small tubercles, especially on the glabella (trilobite anatomy), glabella (middle portion of the head). Because of their resemblance to the Ptychopariida in some features, the proetids are included in the subclass Librostoma. Unlike the trilobites of the phacopid suborder Phacopina, whose trilobite eye, eyes are Eye#Apposition eyes, schizochroal, the proetids have the more common holochroal eyes. These eyes are characterized by close packing of biconvex Lens (anatomy), lenses beneath a single corneal layer that covers all of the lenses. Each ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plate Tectonics
Plate tectonics (, ) is the scientific theory that the Earth's lithosphere comprises a number of large tectonic plates, which have been slowly moving since 3–4 billion years ago. The model builds on the concept of , an idea developed during the first decades of the 20th century. Plate tectonics came to be accepted by Earth science, geoscientists after seafloor spreading was validated in the mid-to-late 1960s. The processes that result in plates and shape Earth's crust are called ''tectonics''. Tectonic plates also occur in other planets and moons. Earth's lithosphere, the rigid outer shell of the planet including the crust (geology), crust and upper mantle, is fractured into seven or eight major plates (depending on how they are defined) and many minor plates or "platelets". Where the plates meet, their relative motion determines the type of plate boundary (or fault (geology), fault): , , or . The relative movement of the plates typically ranges from zero to 10 cm annu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evolution
Evolution is the change in the heritable Phenotypic trait, characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, resulting in certain characteristics becoming more or less common within a population over successive generations. The process of evolution has given rise to biodiversity at every level of biological organisation. The scientific theory of evolution by natural selection was conceived independently by two British naturalists, Charles Darwin and Alfred Russel Wallace, in the mid-19th century as an explanation for why organisms are adapted to their physical and biological environments. The theory was first set out in detail in Darwin's book ''On the Origin of Species''. Evolution by natural selection is established by observable facts about living organisms: (1) more offspring are often produced than can possibly survive; (2) phenotypic variatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paleontology
Paleontology, also spelled as palaeontology or palæontology, is the scientific study of the life of the past, mainly but not exclusively through the study of fossils. Paleontologists use fossils as a means to classify organisms, measure geologic time, and assess the interactions between prehistoric organisms and their natural environment. While paleontological observations are known from at least the 6th century BC, the foundation of paleontology as a science dates back to the work of Georges Cuvier in 1796. Cuvier demonstrated evidence for the concept of extinction and how life of the past was not necessarily the same as that of the present. The field developed rapidly over the course of the following decades, and the French word ''paléontologie'' was introduced for the study in 1822, which was derived from the Ancient Greek word for "ancient" and words describing relatedness and a field of study. Further advances in the field accompanied the work of Charles Darwin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biostratigraphy
Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them.Hine, Robert. "Biostratigraphy." ''Oxford Reference: Dictionary of Biology'', 8th ed., Oxford University Press, 2019. The primary objective of biostratigraphy is ''correlation'', demonstrating that a particular horizon in one geological section represents the same period of time as another horizon at a different section. Fossils within these strata are useful because sediments of the same age can look completely different, due to local variations in the sedimentary environment. For example, one section might have been made up of clays and marls, while another has more chalky limestones. However, if the fossil species recorded are similar, the two sediments are likely to have been laid down around the same time. Ideally these fossils are used to help identify biozones, as they make up the basic biostratigraphy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calcite
Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on the Mohs scale of mineral hardness, based on Scratch hardness, scratch hardness comparison. Large calcite crystals are used in optical equipment, and limestone composed mostly of calcite has numerous uses. Other polymorphs of calcium carbonate are the minerals aragonite and vaterite. Aragonite will change to calcite over timescales of days or less at temperatures exceeding 300 °C, and vaterite is even less stable. Etymology Calcite is derived from the German , a term from the 19th century that came from the Latin word for Lime (material), lime, (genitive ) with the suffix ''-ite'' used to name minerals. It is thus a Doublet (linguistics), doublet of the word ''wikt:chalk, chalk''. When applied by archaeology, archaeologists and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exoskeleton
An exoskeleton () . is a skeleton that is on the exterior of an animal in the form of hardened integument, which both supports the body's shape and protects the internal organs, in contrast to an internal endoskeleton (e.g. human skeleton, that of a human) which is enclosed underneath other soft tissues. Some large, hard and non-flexible protective exoskeletons are known as mollusc shell, shell or armour (anatomy), armour. Examples of exoskeletons in animals include the arthropod exoskeleton, cuticle skeletons shared by arthropods (insects, chelicerates, myriapods and crustaceans) and tardigrades, as well as the corallite, skeletal cups formed by hardened secretion of stony corals, the test (biology), test/tunic of sea squirts and sea urchins, and the prominent mollusc shell shared by snails, bivalvia, clams, tusk shells, chitons and nautilus. Some vertebrate animals, such as the turtle, have both an endoskeleton and a turtle shell, protective exoskeleton. Role Exoskeletons c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in amber, hair, petrified wood and DNA remnants. The totality of fossils is known as the ''fossil record''. Though the fossil record is incomplete, numerous studies have demonstrated that there is enough information available to give a good understanding of the pattern of diversification of life on Earth. In addition, the record can predict and fill gaps such as the discovery of '' Tiktaalik'' in the arctic of Canada. Paleontology includes the study of fossils: their age, method of formation, and evolutionary significance. Specimens are sometimes considered to be fossils if they are over 10,000 years old. The oldest fossils are around 3.48 billion years to 4.1 billion years old. Early edition, published online before prin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Class (biology)
In biological classification, class () is a taxonomic rank, as well as a taxonomic unit, a taxon, in that rank. It is a group of related taxonomic orders. Other well-known ranks in descending order of size are domain, kingdom, phylum, order, family, genus, and species, with class ranking between phylum and order. History The class as a distinct rank of biological classification having its own distinctive name – and not just called a ''top-level genus'' ''(genus summum)'' – was first introduced by French botanist Joseph Pitton de Tournefort in the classification of plants that appeared in his '' Eléments de botanique'' of 1694. Insofar as a general definition of a class is available, it has historically been conceived as embracing taxa that combine a distinct ''grade'' of organization—i.e. a 'level of complexity', measured in terms of how differentiated their organ systems are into distinct regions or sub-organs—with a distinct ''type'' of construction, whic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arthropod
Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metamerism (biology), metameric) Segmentation (biology), segments, and paired jointed appendages. In order to keep growing, they must go through stages of moulting, a process by which they shed their exoskeleton to reveal a new one. They form an extremely diverse group of up to ten million species. Haemolymph is the analogue of blood for most arthropods. An arthropod has an open circulatory system, with a body cavity called a haemocoel through which haemolymph circulates to the interior Organ (anatomy), organs. Like their exteriors, the internal organs of arthropods are generally built of repeated segments. They have ladder-like nervous systems, with paired Anatomical terms of location#Dorsal and ventral, ventral Ventral nerve cord, nerve cord ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extinction
Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and recover. As a species' potential Range (biology), range may be very large, determining this moment is difficult, and is usually done retrospectively. This difficulty leads to phenomena such as Lazarus taxon, Lazarus taxa, where a species presumed extinct abruptly "reappears" (typically in the Fossil, fossil record) after a period of apparent absence. Over five billion species are estimated to have died out. It is estimated that there are currently around 8.7 million species of eukaryotes globally, possibly many times more if microorganisms are included. Notable extinct animal species include Dinosaur, non-avian dinosaurs, Machairodontinae, saber-toothed cats, and mammoths. Through evolution, species arise through the process of specia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
